粉末燃料的沉降速度和最小流化速度分析

Analysis of terminal velocity and minimum fluidization velocity of powdered fuel

粉末燃料输送技术是粉末发动机的核心关键技术之一,目前所用的气动活塞式粉末输送方案还处于概念设计阶段。采用多个经验公式对某密度为2.5g/cm3、粒度为20~300μm的粉末燃料颗粒沉降速度和最小流化速度进行了计算分析,得到流化气温度、压强、颗粒粒度等对最小流化速度的影响规律。分析表明,最小流化速度比沉降速度小得多,按照沉降速度设计流化气速度自然能够满足最小流化速度的要求;高温高压下的粉末沉降速度较常温常压下的小,因此按照粒度较大的颗粒在常温常压下的沉降速度设计流化气速度,就能够同时保证所有颗粒在所有工况下的气力输送,该速度为2.5m/s。

Powdered fuel feeding technique is one of the crucial technologies for powder engine of sorts. Gas fluidization with piston expulsion schematic is still under a stage of concept design so far. In this paper, several experiential formulations were utilized for analysis of terminal velocity and minimum fluidization velocity of a certain powder fuel with density of 2.5 g/cm 3 and particle sizes of 20~300 μm. The impacts of fluidization gas temperature, pressure, as well as particle sizes on minimum fluidization velocity have been summarized. The minimum fluidization velocity of the powdered fuel is much less than its terminal velocity. Therefore, the designed velocity of fluidizing gas on the basis of the terminal velocity automatically fulfils the minimum fluidization velocity requirement. Meanwhile, the terminal velocity under high temperature and high pressure conditions is less than the one under ambient temperature and pressure. Therefore, the velocity of fluidizing gas should be designed on the basis of maximum terminal velocity under normal conditions. It is determined to be 2.5 m/s in this paper.